textproduct: Quad Cities

KEY MESSAGES

- A cold front brings increasing chances of showers and thunderstorms (30-50%) to the area Wednesday. The SPC has a Marginal Risk (Level 1 out of 5) for severe weather along the Highway 20 corridor between Dubuque and Freeport. Primary threats are hail and gusty winds.

- A pattern change is expected this weekend into next week as ridging and southerly flow kick off a warming trend and increase humidity.

SHORT TERM /THROUGH WEDNESDAY/

Issued at 545 AM CDT Tue Jun 23 2026

A closed heights center over Saskatchewan dives southeastward into North Dakota and northern Minnesota today, deepening a weak low pressure system over the Northern Plains. Our winds will shift out of the south during the afternoon and evening ahead of an approaching cold front as mid-to-upper-level clouds start to move in from the northwest. Combining this and the weak WAA, highs will only jump up a few degrees compared to Monday, and the lack of a strong pressure gradient with this system should keep winds light at 5-10 mph. A few isolated showers or storms could develop (10-20%) along and north of the I-80 corridor this afternoon and evening as MLCAPE reaches 250-500 J/kg per latest CAMs.

By tonight, the low pressure translates into Minnesota and Wisconsin, and the cold front moves into northern Iowa. Scattered showers and storms will attempt to reach our northwestern CWA, but associated rainfall will struggle to reach the ground due to dry air still present in the low levels. Regardless, the additional cloud cover and southerly flow are expected to bump lows up by 5-7 degrees into the upper 50s and low 60s.

On Wednesday, the cold front finally reaches the Interstate 380 and Highway 20 corridors in the morning, and sufficient low level moistening will allow for scattered (30-50%) showers and thunderstorms to develop north of Interstate 80 with more isolated coverage (10-30%) south. The weak convergence along the front and the lack of strong upper-level support (i.e., the positive tilt of the trough and mostly unidirectional flow aloft across the area) are anticipated to prevent widespread activity, but there is a decent chance (40-70%) for SBCAPE values to exceed 1000 J/kg along and east of the Mississippi River from daytime heating and dew points rebounding into the 60s along the front. This is why the SPC has issued a Marginal Risk (Level 1 out of 5) for severe weather along the Highway 20 corridor between Dubuque and Freeport where the 0-6 km bulk shear will likely (60-80%) exceed 35 knots. Primary threat with these storms is currently hail, but some gusty winds cannot be ruled out.

LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/

Issued at 145 AM CDT Tue Jun 23 2026

Wednesday Night-Thursday...The cold front clears the CWA by Wednesday evening as northwesterly flow in the low levels sets in. As the low pressure over Wisconsin propagates into Michigan, weak surface troughing on the backside could keep some lingering light showers around for northwest Illinois and east-central Iowa on Thursday. Meanwhile, the next shortwave ejects into the Central Plains as a low pressure strengthens over northern Texas and the Oklahoma Panhandle. Mid-to-upper-level moisture advection should allow for some clouds to encroach into our CWA, but there is uncertainty in the coverage ranging from partly cloudy to overcast. There is also a low chance (20-30%) for some stratiform rain to impact areas along and south of Highway 34 from a warm front over central Missouri. Regardless of cloud cover and precipitation, the northerly flow will likely (80-100%) keep highs comfortable in the 70s once again.

Friday...The trough over the Central Plains reaches Iowa as the low pressure moves into Kansas and northern Missouri. A little bit of deju vu from last Sunday. While there is uncertainty in the GFS and ECMWF ensembles on the strength of the storm system itself, there is general consensus on another rain shield developing north of the low pressure track. Current guidance has the main axis of this stratiform rain over central and northern Missouri, but the 22.18z ECMWF ensemble run does have PoPs at 40-70% south of Interstate 80. Unlike Sunday though, the threat for excessive rainfall is low.

Saturday-Monday...Saturday should be a mostly dry one as ridging starts to build in over the Northern Plains, enhancing ageostrophic convergence aloft over the Upper Mississippi River Valley. Highs will likely (60-90%) rise into the upper 70s and low 80s as the air mass starts to modify with no major frontal passages. Further west though, the next longwave trough digs into the western CONUS, forcing rather strong pressure falls along the lee side of the Rockies. By Sunday, the ridge shifts to over the Upper Mississippi River Valley, and a high pressure that was anchored over the Great Lakes gets shunted eastward, shifting our winds back to southeasterly between it and the elongated low pressure over the Great Plains. Highs will continue to climb into the 80s areawide (80+% chance) as strong WAA in the low levels kick in. The 22.12z LREF run keeps the ridge over the region heading into Monday as the trough over the West Coast pivots to the Northern Rockies. With the continued southerly flow and no cold front, highs creep towards the 90s with heat indices approaching 100 degrees, especially along and south of Interstate 80 (40-60% chance per the 22.12z LREF run). With the slow propagation speed of this longwave trough, the warming and moistening trend will likely continue into next week with dew points in the low-to-mid-70s.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 545 AM CDT Tue Jun 23 2026

High pressure in control will lead to prevailing VFR and light winds today into tonight. There is a low chance for isolated showers/storms this afternoon and evening north of BRL, but did not mention in the TAFs due to expectation for low areal coverage.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...None. MO...None.